The invention generally relates to metal air electrochemical cells.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material. In order to prevent direct reaction of the anode material and the cathode material, the anode and the cathode are electrically isolated from each other by a separator.
When a battery is used as an electrical energy source in a device, such as a cellular telephone, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
In a metal air electrochemical cell, the cathode contains a material that can catalyze the reduction of oxygen which enters the cell as a component of atmospheric air passing through one or more access ports in the container. Zinc oxide, or zincate, is formed in the anode. Thus, the overall electrochemical reaction within the cell results in zinc metal being oxidized to zinc ions and oxygen from the air being reduced to hydroxyl ions. While these chemical reactions are taking place, electrons are transferred from the anode to the cathode, providing power to the device.
Metal-air cells require an air plenum between the cell container and the cathode. Since the cathode does not directly contact the inner surface of the container, electrical contact between these two components must be established in some other way.
In addition, because the container must have air access ports to allow air flow, the sides of the container are not sealed. Therefore, to prevent the electrolyte from leaking out, the top and the bottom of the container must be sealed. Many methods for sealing the ends of the containers of metal-air cells include the use of multiple components, such as cups, grommets and rings.